1. Field
The present disclosure generally relates to fabrication of composite laminate structures, and deals more particularly with a method and apparatus for compacting composite plies over contoured surfaces.
2. Background
During the fabrication of composite laminate structures, it is sometimes necessary to form and compact composite plies over highly contoured tools. For example, in order to fabricate blade type stringers used the aircraft industry, plies may be formed and compacted over a 90° outside radius on a tool.
Several techniques have been used in the past to form and compact plies over contoured tools, but each has disadvantages. Hand-layup and sweeping the plies is possible, but is slow, labor intensive, non-calibrated and may be inaccurate and/or unreliable. Plies may also be laid up and compacted using automated composite tape laying machines which use an integral roller to compact the tape, however these machines are expensive and may not apply even pressure over the width of the tape. Vacuum bags may be employed to compact composite plies over contoured tools, however difficulties may be encountered in achieving even compaction pressure over all areas of the ply. Automated ply sweeping machines have been proposed that use nosepieces to sweep plies over the part profile. However, ply sweeping machines require the use of an intermediate material, such as a low friction sheet between the nosepiece and the ply to prevent distortion and/or smearing of reinforcing fibers caused by the sweeping motion. Installation of the sheet adds to processing time and labor. Moreover, the intermediate material is a consumable item that increases production costs.
Accordingly, there is a need for a method and apparatus for compacting composite plies on contoured tools that avoid the need for ply sweeping, and which are capable of applying uniform compaction pressures. There is also a need for a method and apparatus of the type mentioned above that are capable of maintaining application of a long, uninterrupted line contact compaction force over a contoured tool area.